This invention relates to a method of periodically sanitizing the plumbing in a hot water supply system.
Most buildings are provided with a hot water supply system. Typically, a hot water supply system includes a pump for delivering water into a hot water tank. From the hot water tank, the water can be delivered to a downstream user such as a faucet, etc. The water delivered to the downstream user has a temperature that is generally set as desired by an occupant of the building.
Recently, the assignee of the present invention has developed a system wherein the water is heated in a heat exchanger, with the heat exchanger being provided with a heat source from a refrigerant cycle. There is a water storage tank with a pump delivering a cool water to be heated to the heat exchanger. The cool water is stored in the water storage tank. The hot water, having been heated at the heat exchanger, is also supplied to the tank. As known, the hot water will tend to keep separate from the cool water within the water storage tank. The pump is situated such that it generally draws the cool water to be sent through the heat exchanger.
A supply for delivering the hot water to the downstream user is situated such that it is likely to communicate with hot water when the water storage tank has hot water. A sensor within the water storage tank senses when there is a desired amount of hot water, and stops operation of the pump once there is sufficient hot water in the water storage tank. Typically, some percentage of the water storage tank would be full of hot water before the pump will be shut down. As an example, perhaps 80% of the water storage tank would be hot water with 20% remaining as cold water when the pump is stopped.
One problem with this type of system is there will be a likelihood of stagnant water between the water storage tank and the pump. This stagnant water will be cool, and included pipes will typically not be exposed to any hot temperature water. At the heat exchanger, and downstream of the heat exchanger, there is of course the hot water flow that will sanitize the pipes. However, there is a potential concern with sanitizing the pipe leading from the water storage tank to the pump, in the pump, and from the pump to the heat exchanger.